Figure 7.1. Milk production by Holstein cows, 1987-1991.
In general, it is assumed by researchers and dairy producers that rnilk yield will be lower for cows on an intensive grazing system compared to a dry-lot system; however, the major economic motivation for implementing an intensive grazing system is to lower input costs. Although milk yield may be lower, the lower input costs are projected to result in a respectable income per animal or land unit. Various indices for profitability can be used to evaluate a dairy enterprise, but "milk sales" is the most significant contributor to the income side of profitability. Milk production patterns observed during the project will be discussed in this chapter.
From the onset of the project, the herd was enrolled in an official test program with the Dairy Herd Improvement Association (DHIA). A standard program was used, not an a.m./p.m. program. Generally speaking, cows were in milk from April through December. Actual DIM for each cow were calculated on each DHI test date, and data were divided into 30-day increments, based on DIM, for graphic purposes. The distribution of cows by age and year of the project is provided in Table 7.1.
Milk yield was considerably lower in 1987 than for other years (Table 7.2) because forage growth got ahead of harvesting schedules and all animals were in their first lactation. The mature equivalent (ME) production was also lower during 1987, probably because of lower than desirable genetic merit of the cows purchased from multiple sources. Milk yields generally increased in 1988 above 1987 levels; however, increases in herd production were stymied by all cows being in their first or second lactation and the limited forage available because of the severe drought. Actually, the adjusted rolling herd average (RHA) milk yield for the Jersey cows decreased in 1988 compared to 1987. This and the lower improvements in other production indices for the Jersey cows in 1988 can be at least partially attributed to the grain feeding program - the 1:4 grain-to-actual milk ratio used for both breeds would favor the Holstein cows.
The RHA milk yields in 1989 increased above 1988 levels, but daily and ME milk yields remained very similar or even slightly decreased. The grain feeding regime in practice and forage quantity and quality during 1988 permitted the cows to become quite thin, which may have affected the performance in 1989.
By 1990 and 1991, milk production had reached levels that had been anticipated at the onset of the project. The performance in these two years can be attributed to better forage quality, changes in grain feeding, and improved animal genetics. The RHAmilk production during these two years was also affected by the increase in DIM. The ME milk production for 1991 increased above 1990 levels by 3.7% for Holstein cows and 9.6% for Jersey cows, slightly more than the 2 to 3% annual U.S. average increase in milk yield per cow.
The RHA milk production during 1991 was similar to the 1991 Ohio DHIA averages for milk production (Holstein - 8,537 kg or 18,781 lb; Jersey - 5,707 kg or 12,555 lb). At first glance this may not be apparent because an adjustment must be made for DIM. If you assume a 305-day lactation, the Holstein cows were in milk about 9% fewer days and the Jersey cows were in milk about 8% fewer days than would occur for a typical lactation. Therefore, the following calculations must be made to fairly compare production to the state average:
Holstein: [(7,658 kg/.91)/8,537 kg] x 100 = 98.6% of state average
Jersey: [(5,561 kg/.92)/5,707 kg] x 100 = 106% of state average
Cows typically peaked on the second DHIA test, approximately 60 DIM (Figures 7.1 and 7.2). The Holstein cows essentially peaked at the first DHIA test in 1989 (Figure 7.1), possibly because of the less than desirable body condition discussed earlier. The Jersey cows peaked at the first DHIA test in 1988, perhaps because of the grain feeding regime also discussed earlier. Otherwise, the patterns for the lactation curves were as would be expected for any other herd.
Figure 7.1. Milk production by Holstein cows, 1987-1991.
Figure 7.2. Milk production by Jersey cows, 1987-1991.
Percentages of milk fat and protein were slightly lower than for respective breed averages, especially during 1987 and 1991. Of course, this is somewhat expected with pasture systems; however, feeding programs must be continually investigated to help offset such occurrences. Across all years, the average milk fat-to-protein ratio was similar to breed averages (Holstein - 1.14; Jersey - 1.26); however, the milk fat/protein ratio was high in 1988 for the Holstein cows. This occurred because of an increase in milk fat percentage rather than a decrease in milk protein percentage, perhaps in response to lack of energy intake and an increase in mobilization of fat from adipose tissue.
Milk fat and protein percentages by DIM generally followed patterns similar to other herds (Figures 7.3 to 7.6). Graphing milk fat and protein percentages of DHIA herds by month of the year would usually reveal a rather constant milk composition because cows from all stages of lactation would be used to calculate the averages by month. The cows on this project calved within a short time, and therefore, graphing the herd's milk composition by month also reflects the expected changes in milk composition by stage of lactation.
Figure 7.3. Percentage of milk fat within a lactation for Holstein cows, 1987-1991.
Figure 7.4. Percentage of milk fat within a lactation for Jersey cows, 1987-1991.
Figure 7.5. Percentage of milk protein within a lactation for Holstein cows, 1987-1991.
Figure 7.6. Percentage of milk protein within a lactation for Jersey cows, 1987-1991.
Percentage of milk fat was typically lowest at 120 DIM for Holstein cows (Figure 7.3), corresponding primarily to the month of July when forage quality decreased, forage intake decreased, and grain-to-forage intake increased. Percentages of milk fat for the Jersey cows were somewhat more erratic (Figure 7.4) but were generally lowest during June to August. The percentages of milk fat were particularly low for both breeds during 1987 (first year of project) and 1988 and 1991 (drought years). Milk protein percentages followed patterns similar to those of milk fat, although the magnitude of change was less.
In conclusion, the production patterns for this herd were similar to those of other Ohio herds. However, focus must continue on improving fat and protein production by cows on pasture, especially protein given the current trends in milk pricing programs. The performance of the animals in a pasture system is greatly affected by the quality of available forage and the grain feeding strategy. Although the desire is to maximize the utilization of forage, feeding strategies with the forage and grain must be adjusted as needed when forage production is altered due to environmental effects. This need also gives credence to the fact that using a pasture system does not dismiss the need to test forages.
Actual milk production from a dairy enterprise, organized similarly
to the one on this project, should not be the major index for
measuring success. Rather than comparing production to typical DHIA
averages, use adjustments discussed in this paper. A farmer should
use profitability per animal or land unit as the economic principle
for success instead of productionper animal. However, for new users
of an all-pasture forage system, it is suggested to employ a
conservative estimate of milk production (about 80% of budgeted
amount) for the first year on the system because of the adjustments
in management that will occur until more experience is gained.